Positionable linear friction lock assembly

ABSTRACT

An infinitely positionable linear friction lock assembly utilizes a single friction spring coaxially disposed about a translating rod within an elongated housing. A bias bushing is provided for slidably supporting the rod. The bushing defines a sloped shoulder against which the friction spring hears, with the angle of the shoulder calibrated to provide an increased holding force up to a predetermined axial force on the rod, and permitting the rod to slip at greater axial forces without disturbing the integrity of the spring or its coils. The assembly includes a release or actuation lever having a cap bushing integrated therein to support the rod and keep the actuation lever in alignment.

BACKGROUND OF THE INVENTION

[0001] The present invention concerns positionable linear mechanical locking devices most particularly of the type used for vehicle seating. Specifically, the invention relates to a type of device in which a friction brake is used to restrict axial translation of a positionable rod. In the case of this invention, the friction brake is a coiled spring having an inside diameter smaller than the coaxially located rod, allowing the spring to grip the rod, thereby preventing axial translation of the rod relative to the spring and the housing containing it.

[0002] Infinitely positionable linear friction lock assembly are known in the art. This type of lock generally has an elongated cylindrical rod extending through a housing that contains a pair of coiled springs. The rod can be locked with respect to the housing so that axial translation of the rod is prevented. In certain friction lock this is accomplished by a pair of coiled springs wrapped around the rod each having an free state inside diameter that is smaller than the outside diameter of the rod. To allow translation of the rod, an actuator is connected to an end of each spring. The actuator partially unwinds each springs by expanding their diameters, thereby reducing their gripping force of the springs and freeing the rod to slide through the springs.

[0003] A locking device of this type is included in the seat lock of U.S. Pat. No. 6,164,419, issued Dec. 26, 2000, to Tribbett. As shown in FIG. 2 of the Tribbett patent, the positioning rod passes through an actuating release lever. The lock provides adjustable movement of a seat back relative to a seat frame by actuating the lever to release the coil springs from the rod. In such an application, a very large holding force is required in both directions of rod translation. The resulting housing and its multiple springs and bushings generally exceed 50 millimeters in length. Consequently, a long rod is necessary even if the required range of translation is small.

[0004] Another similar locking device is the friction lock assembly of U.S. Pat. No. 4,457,406, issued Jul. 3, 1984. Although this friction lock assembly, as shown in FIG. 2, requires only one coil spring, the device still requires numerous components, including a pair of carefully machined spring end bushings at each end of the coil spring. Thus, the component count and length of this prior locking device continues to be larger than is desirable for certain applications.

[0005] There are instances in which it is desirable to have a linear friction lock assembling device in which a large holding force is only required in one direction. In addition, it is sometimes desirable that the components of the lock be contained in a relatively small package or envelope. These features are particularly desirable for the adjustment and locking of various positionable members of automotive seating other than the seat itself, such as armrests, headrests and lumbar supports.

[0006] It is desirable in some applications that the positionable locking devices be small in size and have a small component count. It is further desirable for the device to be inexpensive, simple to assemble, and maintenance-free. In many applications, a low unlocking force is all that is needed, allowing the device to be adaptable to many different types of mounting and unlocking systems. It is also desirable that if the holding force is exceeded, the device releases the positionable member without damage to the device.

SUMMARY OF THE INVENTION

[0007] Briefly describing one aspect of the invention, an infinitely positionable linear friction lock assembly includes a positioning rod and a lock assembly that houses a mechanical brake. The housing assembly can include a mounting bracket, and the positioning member can include a flange mounting end. The mounting bracket can be used to mount the housing assembly so the lock can provide adjustment of a member of a vehicle seat or some other device by disengagement of the mechanical brake and translation of the rod.

[0008] The difficulties with prior positionable linear friction lock are overcome in one aspect of the current invention, namely by features of the lock assembly. The lock assembly can accomplish sufficient axial load bearing with a small number of components and a small size. A coil spring contained in a housing can be coaxially wrapped around the positioning rod. The spring has an inner diameter less than the diameter of the rod, allowing the spring to resist sliding on the rod. The spring can be sandwiched between a bias bushing at one end and a spring release mechanism at its other end. A cap bushing can be located at an end of the release lever opposite the spring and mounted in an end of the housing opposite the bias bushing. The cap bushing receives and aligns the release mechanism, retaining it in the housing. Both the bias bushing and the cap bushing can have an inner cylindrical surface acting as a bearing surface for the rod.

[0009] The housing is preferably mounted to a vehicle seat and the flange end of the rod is attached to an adjustable component. The lock prevents adjustment of the component because the coil spring normally prevents the rod from translating in the housing. The component can be released for adjustment by actuating the release mechanism. Actuation of the release mechanism unwinds one end of the spring, releasing the spring from the rod surface and allowing the rod to translate axially through the housing, and thereby releasing the component attached to the rod.

[0010] In one embodiment of the invention, the lock assembly includes a bias bushing having an inner bearing surface for receiving the rod therethrough. In one aspect, the bushing defines a counterbore having an obliquely sloped shoulder at the base of the counterbore for receiving and contacting an end of the coil spring. The shoulder is sloped at a predetermined angle relative to the longitudinal axis of the bore in the bias bushing (and therefore, the axis of the rod). The incline of the sloped shoulder is calibrated to accomplish a maximum axial load that can be held by the lock assembly as the rod presses the coil spring against the spring seat. Specifically, an incline can be specified that opens the spring slightly and allows the rod to slip through the spring at an axial load above a predetermined level without risk of dislodgment of the spring or overlapping of the spring coils.

[0011] In another aspect of the invention, each end of the coil spring has a tang formed by bending a short portion of the spring end radially outward. The tang at one spring end extends into a slot defined by the bias bushing, securing the spring relative to the housing. The other spring end is engaged by the release mechanism that slightly, rotationally unwinds the spring relative to the housing and rod.

[0012] In one embodiment, the release mechanism can include a C-shaped tube portion for receiving an end of a coil spring and a lever portion for actuating the tube portion. The tube portion can further define a slotted notch for compressing the spring against the bias bushing located at the opposite spring end. The tube portion can also have a second slotted notch for engaging a tang located at the rotatable spring end.

[0013] In an additional aspect of the invention, the lock assembly includes a cap bushing attached to one end of the housing. The cap bushing can have an inner lip at one end for receiving the tube portion of the release lever. The inner lip also preferably positions the release mechanism within the housing. The cap bushing can also have an inner bearing surface for receiving the rod therethrough and for aligning the rod with the bias bushing.

[0014] In the preferred embodiment, a housing containing a bias bushing, a cap bushing, a coil spring and a release means, preferably measures less than 31 millimeters in length. An in-line, offset, or other mounting bracket can be fixedly attached to the housing to secure it to a seat member, frame, or other device having an adjustable component. Although in the preferred embodiment the components are constructed from steel, the invention also contemplates use of materials such as aluminum, plastic, or other similarly rigid and durable materials.

[0015] In another aspect of the invention, a number of actuating means are contemplated by the invention. These include a cable and cable bracket attached to the housing, the cable connected to and actuating the release lever; a pushbutton that when depressed actuates the release lever; a pinch actuator that pulls the release lever against another bracket or lever mounted to the lock assembly housing; and a rotatable sleeve that rotates about the housing and is attached to the lever so as to actuate it.

[0016] In an additional aspect of the invention, the canting or biasing of the coil spring by the bias bushing sloped spring seat causes the coil spring to have a large holding force in one axial direction of translation of the rod. Furthermore, the incline of the sloped spring seat can be selected to allow slippage of the coil spring on the rod at a predetermined axial slip force, thus preventing damage of the locking assembly and providing continued functioning of the lock assembly under subsequent loads.

[0017] One object of the invention is to provide an infinitely positionable linear friction lock assembly that features a small length along the axis of the positioning rod, yet provides a large enough load capacity for a variety of applications requiring adjustability. Another object of the invention is to eliminate the need for two or more coil springs and two or more spring bias bushings. A further object of the invention is to provide an adjustable chuck/friction feature at assembly that allows the axial bushing alignment to determine the amount of drag applied to the translating rod when the lock is released.

[0018] One benefit of the invention is that the release lever functions as both a spring release mechanism and an end bushing for the coil spring. Another benefit is that the bias bushing can accomplish an override load limit that will allow the rod to translate and provide subsequent functioning of the friction lock assembly. A further benefit of the invention is that the linear friction lock assembly components can be constructed of a variety of inexpensive materials including steel, aluminum, and plastic. The linear friction lock assembly is also capable of accommodating a number of different mounting configurations and a number of different release actuator systems.

[0019] These and other objects and benefits of the invention can be discerned from the following written description taken together with the accompanying figures.

DESCRIPTION OF THE FIGURES

[0020]FIG. 1 is a perspective view of an infinitely positionable linear friction lock assembly according to one embodiment of the invention.

[0021]FIG. 2 is a partially cut away perspective view of the lock housing portion of the assembly shown in FIG. 1.

[0022]FIG. 3 is a side cross-section view of the assembly shown in FIG. 1.

[0023]FIG. 4 is an end view of the assembly shown in FIG. 1, shown from the end with the cap bushing and having the cap bushing removed to better illustrate the details of the spring and lever on the interior of the housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates.

[0025] The present invention relates to positionable linear friction lock assembling devices and is particularly suited for use in vehicle seating applications. Although the preferred embodiment is envisioned for use in adjusting various members of automotive seating, the principles of the invention can be employed in a variety of applications in which an infinitely positionable friction lock assembly can be utilized.

[0026] In general terms, the invention provides for positioning and locking of a rod that extends through a lock assembly. By mounting one of the rod or lock assembly to a member of a seat, and attaching the other component to another member of the seat, the two seat members can be positioned and locked relative to each other by the inventive friction lock assembly. By simply releasing the locking means contained within the lock assembly, the members can be adjusted relative to each other and then relocked when the lock assembly is re-engaged. With this general background, further details of the invention will be disclosed with specific references to feature numbers and to figures.

[0027] Referring first to FIG. 1, a preferred embodiment of the positionable friction lock assembly includes a lock assembly 50 and a positioning rod 30. The lock assembly 50 can include a housing 51, a bias bushing 70, a coil spring 80, a release mechanism 90, and a mounting bracket 40. The lock assembly 50 can also include an end cap bushing 60 and a cable actuator bracket 100.

[0028] The rod 30 is preferably an elongated cylindrical steel rod having a mounting flange 32 at one end. The bracket 40 and flange 32 can be respectively engaged to seat members that are intended to be adjustably relatively positioned. The housing 51 is preferably cylindrical in shape and can have a window 55 along the length of the housing through which a portion of the release mechanism 90 extends.

[0029] Referring now to FIGS. 2 and 3, the bias bushing 70 is preferably mounted on attached to the inside of one end of the housing 54. The bias bushing 70 defines a bore 75 therethrough that is sized for slidably receiving the positioning rod 30. One end the bias bushing 74 also defines a counterbored spring seat 72, shown most clearly in FIG. 3. The base of the counterbored spring seat 72 forms a sloped shoulder 76 that inclines the spring seat 72 from a shallow end at the bushing top 74 to a deep end at the bushing bottom 73. The shoulder 75 is sloped at a predetermined angle relative to the longitudinal axis of the bore 75.

[0030] The spring seat 72 is sized to receive a first end 81 of the coil spring 80. The coil spring body 83 is positioned around and coaxial with the positioning rod 30. The spring 80 preferably has a normal or free-state inside diameter that is smaller than the outside diameter of the rod 30. With the relative diameters sized in this way, each coil of the spring 80 normally grips the rod 30 and resists translation of the rod relative to the spring.

[0031] When an axial load is applied on the rod 30 in one direction, the first end of the spring 81 is compressed against the sloped shoulder 76 of the bias bushing 70. The sloped shoulder 76 asymmetrically compresses the spring 80 against the rod 30 creating an increased gripping force of the spring upon the rod. The gripping force of the spring 80 on the rod 30 and the first spring end 81 compressing against the bias bushing 70 will inhibit translation of the rod relative to the lock assembly 50.

[0032] One inventive feature of the friction lock 50 is that the lock can have a predetermined axial slip force calibrated by the angle of incline of the shoulder 76. This angle can be selected to be high enough relative to the first spring end 81 so that the lock assembly 50 will inhibit translation of the rod 30 upon application of an axial load on the rod in a first direction up to the predetermined axial slip force. However, the same selected incline of the sloped shoulder 76 will limit the asymmetrical compression of the first spring end 81 by the sloped shoulder 76, so that the rod 30 will slip through the spring body 83 upon application of an axial force on the rod in the first direction that exceeds the predetermined axial slip force. Moreover, the calibrated angle will allow the rod to overcome the frictional holding force of the spring coils without dislodging or damaging the spring, and without dislodging or damaging the spring, and without allowing successive coils to overlap, thereby destroying the lock assembly.

[0033] The angle of incline of the sloped shoulder 76 can range between 10° and 30° from a line perpendicular to the axis of the bias bushing bore 75. However, the angle of incline of the sloped shoulder 76 is preferably approximately 25° or less from the line perpendicular to the axis of the bias bushing bore 75. By selecting an angle of incline of approximately 25° or less, an inventive override feature can be achieved. Although a peak load capacity of at least 900 pounds can be achieved in the specific illustrated embodiment, when the predetermined axial slip force for the selected sloped shoulder 76 incline angle is exceeded, the rod 30 will slip through the spring 80 and lock assembly 50 without damage to the lock assembly components or without disrupting the integrity of the spring or the spring coil. The friction lock assembly will therefore continue to function normally.

[0034] In the preferred embodiment, the first spring end 81 is secured from rotating within the housing 51. The spring 80 preferably has a first tang 81 protruding radially outward from the spring body 83 and located at the first end of the spring. The bias bushing 70 can have a first catch 77 for engaging the first spring tang 81. In the preferred embodiment, the first catch is an axial slot 77 along an inside wall of the counterbored spring seat 72 as shown in FIGS. 2 and 3. The axial slot 77 will allow the first spring end 81 to translate axially relative to the bias bushing 75 as it is asymmetrically compressed at an angle against the sloped shoulder 76. However, the axial slot 77 will prevent the first spring end 81 from rotating relative to the bias bushing 70.

[0035] The inventive friction lock assembly 50 comprised of at least the housing 51, the bias bushing 70, and the spring 80, and can be preferably less than 31 millimeters long. Thus, the assembly is especially suited for applications in vehicle seating that require a small profile and a lower load capacity. Envisioned applications include, but are not limited to, positionable members of automotive seating, for example: armrests, headrests, and lumbar supports.

[0036] In order to easily reposition the rod 30 relative to the lock assembly 50, a release mechanism 90 can be included in the preferred embodiment. The release mechanism 90 applies an unwinding torsion on the second end 82 of the spring 80. The release mechanism 90, as shown in FIG. 2, preferably includes a C-shaped tube portion 93 connected to a lever portion 91. The tube portion 93 receives the second spring end 82 and has a first slotted notch 96, or “kick-in,” for contacting the second end of the spring 80, as best seen in FIG. 3. The release mechanism 90 also includes a second catch 92 for engaging a second tang 82 protruding radially outward from the spring 80 at the second spring end. When the lever portion 91 of the release mechanism 90 is actuated, the tube portion 93 rotates about the axis of the spring body 83, applying an unwinding torsion to the spring 80 via the second catch 92 and displacing the second spring tang 82. The unwinding torsion increases the inside diameter of the spring body 83 to a diameter that is larger than the outside diameter of the rod 30, thereby permitting axial translation of the rod. In the preferred embodiment, the first and second spring tangs are located 180° circumferentially apart.

[0037] In addition to the first slotted notch 96 protruding across an interior segment of the tube portion 93 of the release mechanism 90, the tube portion can also define slots 97 extending along a segment of the circumference of the tube portion. The second catch is preferably a slotted notch 92 punched into the release mechanism 90 at the junction of the tube portion 93 and the lever portion 91. The lever portion 91 of the release mechanism 90 preferably protrudes from the interior of the housing 51 through the housing window 55. The width of the housing window 55 along a portion of the circumference of the housing 51 must be wide enough to provide sufficient travel of the lever portion 91 so that the second spring tang 82 is displaced enough to allow the rod 30 to slip through the spring body 83.

[0038] Although a number of actuating means are contemplated to actuate the lever portion 91, the preferred embodiment includes a cable actuator bracket 100 for connecting a cable actuator to the lock assembly 50. As shown in FIG. 4, the cable actuator bracket 100 can have a loop portion 106 for attaching the bracket to the housing 51 and a back portion 108 forming a first and second notch 103 and 104, a first and second post 101 and 102, and a tie 105 for terminating a cable housing. The bracket 100 back portion 108 is strengthened by bracket side walls 107. The lever portion 91 also has a cable slot 95 and a bent portion forming a hook 94, both for connecting an actuating cable. Actuating the cable will, therefore, rotate the release mechanism 90 relative to the housing 51, unwinding the coil spring 80, and freeing the rod 30 to translate through the lock assembly 50.

[0039] The preferred embodiment can also include an end cap bushing 60 as depicted in FIGS. 2 and 3. The cap bushing 60 is preferably attached to an interior end of the housing opposite the bias bushing 70. The cap bushing 60 has a bore 65 defined therethrough that is sized to receive the rod 30. At the exterior end 61 of the cap bushing 60, the bore 65 can have a chamfer 62.

[0040] In addition to supporting the rod 30, the end cap bushing 60 provides for alignment of the tube portion 93 of the release mechanism 90 within the lock housing 51. The end of the cap bushing 60 opposite the exterior end 61 has a lip 64 on the interior of the bushing and a shoulder 63 defined by the exterior of the bushing. The lip 64 and shoulder 63 are sized to couple with the tube portion 93. The tube portion 93 rotates around the outside of the lip 64, thereby centering the tube portion within and away from the interior of the housing 51. The end cap bushing 60 also serves to sandwich the tube portion 93 between the end cap bushing 60 and the spring 80.

[0041] Placement of the end cap bushing 60 in the housing 51 at assembly of the lock assembly 50 determines the amount of bias compression on the spring body 83 as the spring 80 is compressed between the first slotted notch 96 of the tube portion 93 and the sloped shoulder 76 of the bias bushing 70. Axial alignment of the end cap bushing 60 with the bias bushing bore 75 also provides for smooth translation of the rod 30 when the release mechanism 90 is actuated.

[0042] Another feature of the inventive friction lock assembly is the lock assembly 50 mounting bracket 40, as depicted in FIGS. 2 and 4. The mounting bracket 40 can have a flat bracket body 43 having tab holes 46 for receiving tabs 52 extending from the housing 51. The tabs 52 preferably pass through the tab holes 46 and are crimped around the bracket body 43, fastening the bracket 40 to the housing 51. Extending from the bracket body 43 can be a first and second ear 41 and 42 having mounting holes 45 for mounting the lock assembly 50 to a member of a seat. Alternatively, the mounting bracket 40 can be attached to the housing 51 by other fastening means, for example, welding. Other methods known in the art of mounting the lock assembly 50 to a member of the seat are also contemplated by the present embodiment of the invention.

[0043] The positioning rod 30 can have a flange end 33 having a mounting flange 32 with a flange hole 34 defined therethrough and a neck portion 31 at the junction of the mounting flange and rod. The mounting flange 32 is for connecting the positioning rod 30 to a member of the seat. The end of the rod 35 opposite the flange end 33 can have a radius 36 or chamfer, removing the sharp outer circumference of the rod end.

[0044] Although in the various components are preferably constructed from steel, the invention also contemplates use of other rigid, durable materials such as aluminum, plastic and tubular steel.

[0045] Anticipated applications that require a large holding capacity in only one direction allow the inventive friction lock assembly to contain fewer components and to be smaller in size. Specifically, the preferred embodiment contains only one coil spring 80 and one machined bias bushing 70 having an inclined sloped shoulder 76. Previous friction lock assembly required a pair of coil springs and/or a pair of matched bias bushings. In order to further overcome the problem of numerous components and excessive lock size, the release mechanism 90 feature provides an easily constructed, compact, and inexpensive method of both disengaging the lock and of supporting the second end of the coil spring 80. These features and other inventive aspects of the invention provide distinct advantages over other linear friction lock assembly devices. For example, the sloped shoulder 76 of the bias bushing bore 75 and the first slotted notch 96 of the tube portion 93 of the release mechanism 90 provide spring biasing and a predictable load capacity for a predetermined axial slip force. Applied loads above the predetermined slip force will cause the rod 30 to slip through the spring 80, protecting the friction lock assembly components from damage.

[0046] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. 

What is claimed is:
 1. An infinitely positionable linear friction lock assembly having a predetermined axial slip force, the lock comprising: a housing; a bias bushing engaged to said housing, said bushing defining a bore therethrough, the bore defining a longitudinal axis, and said bushing further defining a spring seat at one end of said bore, said spring seat including a sloped shoulder; a rod slidably extending through said bore of said bushing along said longitudinal axis; a coil spring positioned around and coaxial with said rod, said spring having a normal inside diameter smaller than the diameter of said rod, said spring having a first end in contact with said sloped shoulder; said sloped shoulder inclined relative to said longitudinal axis at an angle sized to asymmetrically compress said spring on said rod, upon application of an axial force on said rod in a first direction less than a predetermined axial slip force, said angle further sized to maintain the integrity of the spring while allowing the rod to slip through the spring upon application of an axial force or said rod greater than said predetermined axial slip force.
 2. The infinitely positionable linear friction lock assembly of claim 1, wherein: said predetermined sloped shoulder is between 10 and 30 degrees.
 3. The infinitely positionable linear friction lock assembly of claim 2, wherein: said sloped shoulder is preferably less than 25 degrees from perpendicular to axis of said rod.
 4. The infinitely positionable linear friction lock assembly of claim 2, wherein: said sloped shoulder is approximately 25 degrees from perpendicular to axis of said rod.
 5. The infinitely positionable linear friction lock assembly of claim 2, wherein: said coil spring has a first tang at said first end of said spring, said first tang protruding radially outward from said spring; and said bias bushing has a first catch, said first catch engaging said first tang.
 6. The infinitely positionable linear friction lock assembly of claim 5, wherein: said first catch is an axial slot defined in said spring seat.
 7. The infinitely positionable linear friction lock assembly of claim 6, wherein: said bias bushing is fixedly engaged at one interior end of said housing; and
 8. The infinitely positionable linear friction lock assembly of claim 7, further comprising: a release mechanism defining an opening for engaging a second end of said spring and having a lever for actuating said release mechanism, to applying an unwinding torsion to said spring.
 9. An infinitely positionable linear friction lock assembly comprising: a housing; a bias bushing engaged to said housing, said bushing defining a bore therethrough and defining a counterbored spring seat at one end of said bore; a rod located through said bore of said bushing; a coil spring positioned around and coaxial with said rod, said spring having a normal inside diameter smaller than the diameter of said rod, said spring having a first end in contact with said spring seat; and a release mechanism defining an opening for engaging a second end of said spring and having an actuator for applying an unwinding torsion to said spring.
 10. The infinitely positionable linear friction lock assembly of claim 9, wherein: said coil spring has a first tang at said first end of said spring and a second tang at said second end, said tangs protruding radially outward from said spring ends; said bias bushing defining a first catch for receiving said first tang; said release mechanism defining a second catch for contacting and rotationally displacing said second tang upon actuation of said actuator, whereby said second catch applies an unwinding torsion to said spring, increasing the inside diameter of the spring, and permitting axial translation of said rod.
 11. The infinitely positionable linear friction lock assembly of claim 10, wherein said release mechanism further comprises: a C-shaped tube portion for receiving said second spring end, said tube portion having a first slotted notch protruding across an interior segment of said tube portion and contacting said second spring end; and wherein said actuator is a lever portion attached to said tube portion.
 12. The infinitely positionable linear friction lock assembly of claim 11, further comprising: a window defined by an axial wall portion of said housing, said lever portion protruding from an interior of said housing through said window.
 13. The infinitely positionable linear friction lock assembly of claim 12, wherein: said lever defines a slot for engaging an actuating cable.
 14. The infinitely positionable linear friction lock assembly of claim 12, further comprising: a cap bushing engaged to said housing and having an interior lip at a first end, said lip coupled with said tube portion of said lever, and said tube portion positioned between said second spring end and said cap bushing.
 15. The infinitely positionable linear friction lock assembly of claim 14, wherein said lock assembly measures less than 31 millimeters in length.
 16. The infinitely positionable linear friction lock assembly of claim 12, wherein: said first tang is located 180° relative to said second tang.
 17. An infinitely positionable linear friction lock assembly comprising: a housing; a bias bushing attached at one interior end of said housing, said bushing defining a bore therethrough and defining a counterbored spring seat at one end of said bore, a base of said spring seat defining a sloped shoulder; a rod located through said bias bushing bore; a coil spring positioned around and coaxial with said rod, said spring having a first end in contact with said spring seat; a release mechanism defining a tube portion for receiving a second end of said spring; said release mechanism further defining a lever portion attached to said tube portion and for actuating said tube portion; and a cap bushing attached at an opposite interior end of said housing, said cap bushing defining a bore therethrough and defining an interior lip at a first end of said bore, said lip coupled with said tube portion of said release mechanism, and said tube portion positioned between said second spring end and said cap bushing.
 18. The infinitely positionable linear friction lock assembly of claim 17, wherein: said housing is cylindrical; said cap bushing is positioned in said housing to align said tube portion coupled to said lip with the axis of said housing and to prevent contact of said tube portion with said housing; and said cap bushing is further positioned in said housing to align said cap bushing bore with said bias bushing bore, thereby providing smooth movement of said rod through said bores.
 19. The infinitely positionable linear friction lock assembly of claim 18, wherein: a lock assembly comprised of at least said housing, said bias bushing, said cap bushing, and said coil spring, measures less than 31 millimeters long.
 20. An infinitely positionable linear friction lock assembly having a predetermined axial slip force, the lock comprising: a cylindrical housing, said housing defining a window in an axial wall portion of said housing; a mounting bracket attached to said housing; a bias bushing engaged to a first end of said housing, said bushing defining a bore therethrough and defining a counterbored spring seat at one end of said bore, a base of said spring seat defining a sloped shoulder, said slope shoulder between 10 and 30 degrees from a perpendicular axis to said bore; a rod located through said bore of said bushing, said rod defining a flange end; a coil spring positioned around and coaxial with said rod, said spring having a normal inside diameter smaller than the diameter of said rod, said spring having a first end in contact with said sloped shoulder, said coil spring having a first tang at the first end of said spring and a second tang at a second end of said spring, said tangs protruding radially outward from said spring; said bias bushing having a first catch for engaging said first tang; said sloped shoulder inclined high enough relative to said first spring end to asymmetrically compress said spring on said rod, inhibiting translation of said rod relative to said spring upon application of an axial load on said rod in a first direction, while inclined low enough relative to said first spring end that said rod slips through said spring upon application of an axial force that exceeds the predetermined axial slip force; a release mechanism defining a tube portion for receiving said second end of said spring, said tube portion have a second catch for contacting and rotationally displacing said second tang, said release mechanism also having a lever portion for actuating said tube portion and protruding from an interior of said housing through said housing window; and a cap bushing attached at a second opposite interior end of said housing, said cap bushing defining a bore therethrough and defining an interior lip at a first end of said bore, said lip coupled with said tube portion of said release mechanism, and said tube portion positioned between said second spring end and said cap bushing.
 21. The infinitely positionable linear friction lock assembly of claim 20, wherein said lock measures less than 31 millimeters long. 